1. Field of the Invention
The present invention relates to a camera body, an interchangeable lens, and a camera system including the camera body and the interchangeable lens. More specifically, the present invention relates to a technology for communication between the camera body and the interchangeable lens.
2. Description of the Related Art
A camera system including a camera body and an interchangeable lens is known.
In addition, a camera system is known in which information regarding an inside of an interchangeable lens is transmitted to a camera body and the camera body controls the interchangeable lens by transmitting, to the interchangeable lens, instructions to drive an aperture and lenses in the interchangeable lens on the basis of the information.
Regarding the camera system, in a case where a new interchangeable lens provided with a new function that an existing interchangeable lens does not have is sold, even if the new interchangeable lens is connected to an existing camera body, the new interchangeable lens needs to operate normally. In addition, regarding even a new camera body for the new function, an existing interchangeable lens needs to operate normally when connected to the new camera body.
Accordingly, communication specifications, instructions, etc., between the camera body and the interchangeable lens comply with those that are known. In addition, it is necessary to add specifications and instructions for further new functions.
As communication specifications and instructions are increased whenever a new function is added, the number of instructions is increased. As a result, there is a possibility that 256 types of instructions that can be defined by 8 bits in ordinary serial communication may be insufficient.
In this case, it is necessary to use 16 bits to define instructions. However, another problem occurs in that communication time is increased.
In addition, there is a possibility that data received from a new interchangeable lens may be incorrectly used in an existing camera body.
In this case, it is preferable that the existing camera body, which has a problem, be modified. However, it is difficult to modify the existing camera body because it has already been sold. Accordingly, in many cases, data that may be incorrectly used in an existing camera body is not stored in a new interchangeable lens, and, even in a camera body of a newer model, functions of the camera body are not used. In this case, the number of instructions that can be used decreases, so that the interchangeable lens cannot comply with a new function or performance.
To solve the above problems, Japanese Patent Laid-Open No. 04-273225 discloses the following technology.
In a case where an interchangeable lens for a single-lens reflex camera body is used for a video camera body with interchangeable lenses, even if both are connected to each other by using an adapter capable of mechanical conversion, the interchangeable lens cannot be controlled. This is because the single-lens reflex camera and the video camera completely differ in lens control method.
Accordingly, an adapter is needed that converts data from the interchangeable lens into a format necessary for the video camera body, and that conversely converts a control signal from the video camera body into a format necessary for the interchangeable lens.
However, for the same camera system, connection by using an adapter or the like is not preferable since an optical system is changed and size is increased.